Home theater subwoofer setup

Tips to help you tune up your bass

You've just fired up a Blu-ray movie on your new surround sound system. The screen momentarily goes blank: here comes the main feature. No — it's a THX demo! (You weren't expecting that.) Imaginary objects zip around your head in 3D space...this is promising. And then that famous tsunami-wave of sound, THX's audio "logo".... But wait, where's the bottom-end? Where's the spine-tingling bass?

If your home theater system's bass output sounds too lean, or if it's muddy and distorted, a few key settings on your powered subwoofer and receiver can make all the difference. Here are a few tips to help your sub perform at the top of its game.

Set the crossover point

For the best possible sound, you want your front, center, and surround speakers to play only the frequencies they can handle, and your powered sub to play the rest — the deep bass frequencies. That's the job of your system's crossover. To use a common analogy, a crossover works sort of like a "sonic traffic cop," sending the right frequencies to the right speakers. But where should your sub leave off, and your other speakers begin?

To determine the optimum crossover point for your system, you should know what frequencies your main speakers can handle. In my own system, I've got small satellite speakers all the way around. The owner's manual told me they could go down to about 120 Hz, and I set my system's crossover accordingly. (For larger speakers, this number is usually lower — it's not uncommon for bookshelf speakers to get down to 50 or 60 Hz, for example.) Once you've set your crossover frequency to one that matches your speaker setup, sit back and give a quick listen. You can even experiment by adjusting the crossover frequency a little bit one way or the other...after all, what matters is getting your system to sound good to you.

This Polk Audio subwoofer has a separate unfiltered "LFE" input for use with a home theater receiver.

Check your subwoofer's "LFE" setting

What some folks may not know is that their system probably has two subwoofer crossovers, one inside their home theater receiver and another built into the powered subwoofer itself. And these two crossovers don't play nicely together. If they're both engaged simultaneously, you're probably not getting all the bass that you could.

That's where your subwoofer's "LFE" setting comes in. This acronym stands for "Low Frequency Effects" (not "Loud Family-room Explosion" or "Looking For Explanation"). "LFE" is just the technical name for your home theater receiver's bass channel.

This setting tells your subwoofer whether to use its own built-in crossover or the one inside your receiver. In most cases, the latter is the better way to go. That's because practically all home theater receivers built in the last several years have advanced digital bass management that not only tells your subwoofer what frequencies to play, but also tells the rest of your speakers what frequencies not to play.

If you're using a home theater receiver with bass management, you want to disable your sub's built-in crossover to make sure it plays all the bass frequencies your receiver is sending through its subwoofer output. To do this, be sure to use your receiver's preamp-level subwoofer output, and your subwoofer's LFE input.

Some subs have a switch that lets you toggle between LFE (use this when you have a home theater receiver) and "normal" (use this when you don't). Others have a separate unfiltered LFE input.

Every link in the audio "chain" counts — use a quality subwoofer cable to make sure your sub receives a strong, clean signal.

What if my sub doesn't have an LFE option?

If you have an older receiver or subwoofer, LFE connections may not be an option. In that case, you can use speaker wire to connect to your sub's speaker-level inputs. Or you can go with a line-level connection that uses standard stereo RCA cables. If you use either of these connection methods, turn your subwoofer's crossover dial all the way up to help ensure that it won't interfere with your receiver's built-in bass management.

A few high-end subwoofers and receivers also offer an XLR connection, which is less susceptible to signal degradation. For the most part, you won't have to worry about this type of connection — your sub's owner's manual will be very clear if you should use it.

A quick note for stereo music listening

After the movie's over, you decide to kick back and listen to a new album you bought earlier. You're already familiar with the first track – it's got a killer bass line that should be kicking in... any second now.

If you plan to use your home theater setup for stereo music listening, too, then be aware that not all home theater receivers will send a signal to the LFE output when in stereo mode. Most do, but for those that don't, you'll notice a drop in the low-end when you switch from surround sound to stereo listening. Check your receiver's owner's manual to be sure. If your receiver isn't sending a signal to the LFE output, you can try using line-level or speaker-level connections to bring back the bass.

Customize your sub's sound for your media and your room

Many subs these days can be fine-tuned to match the material you're listening to, or optimized for the acoustics of your particular listening space. For example, your sub may offer presets like Movie, Video Game, Rock Music, Jazz Music, Sports, or Night Listening. You can switch from one to another based on the type of entertainment you're enjoying.

Of course, how and where you place your subwoofer in your room can impact the sound and quality of the bass. For example, subwoofers tucked away in a corner generally produce more bass, but can tend to sound "boomy." So some subwoofers have calibration options for adjusting the sound to fit your room, either by letting you indicate your sub's placement (corner, mid-wall, in-cabinet, etc.) or by taking sound samples and automatically tailoring the sound to suit your room. You can learn more about subwoofer placement in our article on home theater speaker placement.

Find the level that sounds best

Finally, there's your subwoofer's level control. It's a straightforward concept, no doubt. But this setting makes a big difference, so it's worth spending a few minutes tweaking and listening to get it right. Keep in mind that more bass isn't necessarily better bass. Try starting at a lower level and gradually bumping it up to where you're feeling plenty of punch, without sacrificing clarity. If you resist the urge to crank your sub's level control way up past twelve o'clock, you stand a better chance of achieving tight, clean bass, and well-balanced overall sound.

Of course, it's all a matter of taste. I'll admit that, for my own part, I probably tend to push my sub a little bit more than others might. But then again, when I pop in a THX-mastered movie disc, and that huge-sounding THX demo kicks in, it's like audio nirvana.

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Crutchfield Writer Biography

James Ralston

James Ralston is Crutchfield's Web Editor for Home Audio/Video. He joined the company in 1994 as a member of the sales department and began writing about A/V gear in 1999. James attended the University of Virginia, receiving a Bachelor of Arts degree in English Literature. Since arriving in the Charlottesville area, he has been active in the local music scene, playing drums in a variety of musical projects ranging from world beat, to blues, to instrumental improv.